WASHINGTON – A super PAC aligned with Senate Majority Leader Mitch McConnell is unleashing a $6.4 million advertising onslaught on Tuesday as the fall midterm campaign begins in earnest.

The spending blitz by the Senate Leadership Fund includes $1.1 million in advertising in Tennessee, a deep-red state President Donald Trump won by 26 percentage points in 2016. But the Democratic Senate contender, former governor Phil Bredesen, has posted strong poll numbers in his race against GOP Rep. Marsha Blackburn for the Republican open seat, forcing GOP operatives to start spending heavily.

In all, the Senate Leadership Fund has budgeted $60 million for the midterms, according to figures provided first to USA TODAY. A nonprofit arm of the group, One Nation, already has spent $38 million.

Republicans have a narrow 51-49 advantage in the Senate, but Democrats hoping to seize the majority face a tough map in this election. Ten Democratic incumbents are seeking re-election in states Trump won.

In addition to Tennessee, the Senate Leadership Fund is targeting its TV, radio and digital ads in five other states this week, officials told USA TODAY. The group will spend $1.8 million in Missouri, $1.4 million in Indiana, $1 million in Nevada, $800,000 in West Virginia and $350,000 in North Dakota.

In a statement, Steven Law, who runs the super PAC, said Senate Democrats “have made clear their agenda is resistance and repeal of the 2016 election. Even Democrats in pro-Trump states have gone along with their party bosses, and we’re going to hold them accountable for it.”

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Although Republicans have the advantage in November’s Senate races, GOP strategists have expressed concern that Democrats could chart a path to the majority if the GOP stumbles in places such as Texas and Tennessee, where a recent NBC/Marist poll gave Bredesen a slight edge over Blackburn.

“In Tennessee, honestly, Democrats found the one candidate in the entire state that allows them to be competitive here,” said Jennifer Duffy, who analyzes Senate races for the nonpartisan “Cook Political Report.”

But, Duffy said, Democrats “still have a bad map. They have to hold on to some really vulnerable seats.”